feat(immich): declare QSV transcoding via config-file settings

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016e2PKH5yN31h6JgHWCQb32

modules/environments/immich/default.nix

@@ -24,7 +24,13 @@ in
       mediaLocation = "/var/lib/immich";
       machine-learning.enable = true;
       accelerationDevices = [ "/dev/dri/renderD128" ];
-      settings.server.externalDomain = "http://${hostName}:${toString port}";
+      # Setting `settings` puts Immich in config-file mode: the admin settings
+      # UI becomes read-only and system config is managed declaratively here.
+      settings = {
+        server.externalDomain = "http://${hostName}:${toString port}";
+        # Intel Quick Sync hardware transcoding (jupiter's iGPU).
+        ffmpeg.accel = "qsv";
+      };
     };
 
     # The native module does not add GPU groups; required for VAAPI/QSV transcoding.